Filtration system

ABSTRACT

For use in filtering a fluid which is susceptible to light and heavy solids and other materials suspended in the liquid, a filtration system which removes the heavier and lighter suspended particles through settling and skimming whereupon the suction of a downstream pump draws the liquid through the filter apparatus, the filter apparatus functioning after removal of the heavier and lighter contaminants which typically clog filter media, all the apparatus included in an open tank.

United States Patent Holiand 54] FILTRATION SYSTEM [72] Inventor:Richard W. Holland,

Houston, Tex. 77024 [22] Filed: Apr. 28, 1969 [21] App1.No.: 819,845

13103 Conifer,

[52] U.S.Cl ..2l0/104,2l0/121,210/193, 210/298, 210/406 [51] Int. Cl..B0ld 29/24 [58] Field of Search ..210/ 104, 206-208, 210/303, 306,346, 203, 523, 75,121,193, 298, 406

[56] References Cited UNITED STATES PATENTS 448,122 3/1891 Chancellor..210/206 1,800,517 4/1931 Foster ....210/104 2,035,851 3/1936 Walker..210/346 51 3,635,343 [451 Jan. 18,1972

2,540,362 2/1951 Winslow e! a] ..210/306 X 2,678,912 5/1954 Kalinske eta1 .210/523 X 2,919,029 12/1959 Smith ..210/305 3,339,736 9/1967Mu11er... .....210/104 1,716,040 6/1929 Genter... ..210/406 X 3,334,7498/1967 Ladd ..210/298 X Primary ExaminerSamih N. Zaharna Attorney-Dona1dGunn [5 7] ABSTRACT 7 Claims, 8 Drawing Figures PATENTEU JMH8I97Z3,635,343 sum 1 0? 2 FIG.7

Richard W Holland IN VE N TOR A T TORNE Y PATENIED JAN! a 1972 SHEET 2UF 2 FIGS FIG.7

Richard W Holland INVE N TOR A TTORNEY FILTRATION SYSTEM SUMMARY OFPROBLEM AND SGLUTION Filtration equipment commonly available for usewith industrial plant water, process fluids, and pollution controlequipment normally utilizes a filter leaf nest through which thecontaminated fluid is forced under pressure. Typically, this requires apressuretight vessel, an inherently expensive structure built to closetolerances, and equipped with necessary gaskets and other sealingapparatus. Routinely, the fluid to be filtered is forced into the vesselunder pressure and is forced through the filtration media. Inasmuch asthe entire filtration process occurs within a heavy closed vesselmaintained under pressures greater than atmospheric pressure, certainproblems arise with the control and servicing of the equipment. It isparticularly difficult to service the equipment for periodical cleaningof the filtration media.

Optimum filter operation is achieved when the fluid is retained for alength of time prior to reaching the filtration media. Additionally,filtration is enhanced when the cleansed fluid is partially recycledthus increasing the retention time. However, when the fluid isforced'through the media under pressure, the skin formed on the face ofthe filtration media and maintained there by the pressurized flow of thefluid through the filter media materially reduces the efficiency of thefilter and shortens the retention time.

Pressurized filter systems of this type have in the past materiallyincreased the skin formed on the filtration media.

Broadly, two types of contaminants tend to unduly clog the filtrationmedia. Heavier contaminants which are merely carried in the fluid whenpumped under pressure tend to clog the filtration media. Also, lightercontaminants which are dispersed in the fluid, such as oil in water,will likewise clog the filtration system. In either case, the lighterand heavier filtration contaminants are found on the face of thefiltration media where they form a dense skin cake which must beperiodically removed. Inasmuch as the filtration media is intended toremove contaminants, this leads to a material reduced efficiency in theuse of the filtration equipment.

The foregoing has pointed out certain deficiencies found in the priorart. The present invention is summarized as providing an open tankfiltration system which is powered by a suction pump operating at theoutlet of the filtration system, which draws the fluid through theapparatus. Hence, a pressure-type vessel is not required, and moreover,the pump is the sole motive means required for the presentinvention. Thetank includes a coated filter leaf nest which is submerged in the liquidto be filtered. The contaminated fluid is brought into the tank at astilling well which calms the agitated liquid to thereby permit heavysolids suspended in the liquid to settle, the apparatus providing meansfor removing the heavy solids. In the calm environment, the lightermaterials, typically oil in water, float to the surface. The surfaceportions of the liquid are passed through a skimming apparatus whichremoves the lighter contaminants. Through the prior removal of suspendedsolids in the liquid, the skin cake on the filter media is materiallyreduced and typically less clogging even when formed so that theperiodic cleaning is reduced and the power required to draw the liquidthrough the apparatus is measurably reduced. The nonfilteredcontaminants are removed from the filter system using energy derivedfrom the sole pump source. The entire system, being of an open orexposed configuration, permits complete control and servicing of theapparatus with a minimum of effort and cost.

Many objects and advantages of the present invention will become morereadily apparent from a consideration of the included specification anddrawings wherein:

FIG. I is a plan view of the filter system of the present inventionshowing the downstream pump location and other components within thetank;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. I whichshows the relative location of the filter media and a portion of theapparatus which removes the suspended contaminants;

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1 showing.details of the apparatus which dissolves coagulant chemicals in theliquid, if desired;

FIG. 4 is a view of a filter leaf as mounted in the tank;

FIG. 5 is an enlarged view of a support for an individual leaf attachedto the tank rail;

FIG. 6 is an enlarged view of the airliftand surface skimmer shown alsoin FIG. 2;

FIG. 7 is an end view of the skimmer weir taken along the line 7-7 ofFIG. 6; and,

FIG. 8 is an enlarged view of the level control system partly shown inFIG. 3 which illustrates flow control of the liquid to be filtered.

Attention is first directed to FIGS. l and 2 of the drawings whichillustrate the exposed open top tank of the present invention which isindicated by the numeral 10. The filtration system 10 incorporates abottom plate 11 shown in FIG. 2, suitable end plates 12 and I3, andsidewall plates 14 and I5. As will be understood, the tank may beexceedingly large with several sets of filtration apparatus, or may bemeasurably smaller dependent on the circumstances of its installationand operation.

The numeral 16 indicates the influent nozzle which delivers the liquid17 to the filter I0. It will be'understood that the liquid is perhapsloaded with suspended heavy and light particles and impurities. For sakeof explanation, but not as a limitation on the present invention, thepreferred embodiment will be described in operation with water and thelighter contaminants will include oil, the heavier contaminants willinclude silt. The lighter and heavier pollutants will be identified ascontaminants while the filter removes suspended pollutants of anyparticular description. Plant influent and effluent typically have needof filtration of the above general description. However, the apparatusof the present invention may be used with other liquids and pollutants,and the description in conjunction with a plant filter system is not alimitation on the present invention.

The nozzle 16 directs the incoming liquid into a stilling well 18 whichis generally defined by the end wall 13 and a baffle wall 19 immediatelyin the front of the noule 16. The volume of liquid held in the stillingwell 18 is sufficient to have a measurable retention time for eachportion of the liquid introduced to the filter 10. Moreover, the bafflewall 19 extends upwardly to define a portion of the stilling well and isthen connected to a battle grid 20 which separates the portion of theequipment having the filter nest from the stilling well 18. The waterenters the stilling well through the noule I6 and travels quite slowlythrough the baffle grid 20 into the filter means which are indicatedgenerally by the numeral 21 in FIG. 2.

The filter means 21 incorporates a collection header 22 which extendsthrough the end wall 12 toward the battle wall 19. The header 2] iscommunicated with a suction pump 23 powered by a suitable motor 24 whichforces the liquid through a discharge nozzle 25 and into an outletheader 26. A balance valve 27 is located in the header 26 for directingsome of the filtered liquid through a dispersing nozzle 28 which returnsthrough the wall 12 to the filter means 21. The dispersing nozzle isuseful in filter aid sluicing and for recycling a portion of thefiltered liquid to increase the retention time i i the filter. As willbe appreciated, the portion of liquid returned to the filter forrecycling may vary from 0 percent to approaching percent, dependent on anumber of circumstances in the operation of the present invention.

The collection header 22 is preferably a rectangular hollow member asshown in FIG. 4. A number of filter leaves are supported in parallel byparallel tank rails 30 shown in FIG. 5. The tank rail is preferablyformed of angle stock and a leaf clip 31 extends from the tank rail on abolt 32. The leaf clip 31 supports an individual filter leaf 33 as shownin FIG. 5 with a support being provided at the upper leftand upperright-hand comers as shown in FIG. 4. The individual filter leaf 33shown in FIG. 4 is preferably a rectangular filter structure having abottom central drain 34 which plugs into an opening in the collectionheader 22. The drain 34 provides the structural support and alignment ofthe leaf filter 33 in conjunction with the filter clips 31. The leafclip 31 is preferably an inverted U- shaped retainer which clamps thefilter leaf on the front and back faces to true the filter in positionto be parallel with the other filters as shown in FIGS. 1 and 2. Thefilter leaf 33 preferably includes a screen surface 35 which canoptionally be coated with a filtering aid such as a diatomaceousmaterial.

The number of particular filter leaves in the filter nest means 21 isclearly subject to variation dependent on the size of the installationand the cycle time permitted infiltration. Moreover, the apparatus maybe expanded to provide a very substantial measurable surface are offiltration communicating with the collection header 22. Of significanceto the present invention is the fact that the filter clips 31 may bereadily removed, even during operation, and the individual filter liftedout. In FIG. 4, it will be noted that the drain 34 at the bottom of eachfilter 33 preferably rests on a collar which supports it incommunication with the collection header 22. Should an individual filterbe removed, the opening in the header is preferably temporarily pluggeduntil the filter 33 is returned to its position.

The turbulence where the filter elements are located preferably receivesthe liquid after it has been stilled upon operated completely withoutchemical additives as desired. In any event, the chemical additives areplaced in the tank 52 shown in enlarged view in FIG. 8.

The conduit 51 which extends into the tank is directed toward animpeller blade 53. The impeller blade 53 is mounted on a hollowrotatable shaft 54. The shaft passes through a suitable packing gland atthe bottom of the container 52 and extends through the upper wall of theinfluent nozzle 16 and supports a second impeller blade 55. The shaft 54is hollow and is open at its upper end as shown in FIG. 8 in thecontainer 52. Additionally, the shaft 54 is hollow and provides anopening into the noule 16. The conduit 51 is directed toward theimpeller 53 with a view of rotating the shaft 54. The impeller 55located in the influent line is also driven by the flowing liquid. Thetwo impellers together rotate the shaft 54. The impeller 53 in thecontainer 52 stirs and chums the incoming fluid from the line 51 withthe chemical, of whatever nature or form, and, dependent on the settingof the rate valve 50, slight overflow occurs during operation of theequipment. As the level in the container 52 rises, the chemical ladenwater overflows into the pipe 54 and is drawn downwardly into the vnozzle 16. The agitation in the chemical container 52 stirs the flowingthrough the baffle grid 20. Since the extent of turbulence is measurablyreduced, there is some possibility of heavier sediment falling from theliquid in the chamber containing the filtration means 21, and hence, thelower floor 11 is sloped to the right as viewed in FIG. 2 and a hingedflap 35 drains the leaf nest chamber to a waste trough 37. The wastetrough will be considered later in conjunction with other portions ofthe apparatus which remove the heavier and lighter contaminants from theliquid 17.

At this juncture, it is helpful to describe how the liquid 17 enters thefilter apparatus 10. The numeral indicates a level control valve shownin FIGS. 3 and 8. The valve 40 is spring loaded to close and is openedby operation of the cylinder 41. The cylinder 41 operates the controlarm 42 to control fluid flow through the inlet nozzle 16. The ball float43 responding to the surface of the liquid 17 positions a throttlingvalve 44 to vary the pressure range from maximum pump pressure to fullventing with infinite intermediate values in a fluid line 45communicating with the cylinder 41. The valve 44 is a conventionalbought three-way valve with a vent 44a to the tank. The valve 44 ventsfrom the pump 23 or the cylinder 41 causing equilibrium between thespring force and cylinder force. In lieu of the return spring, theupstream or feed pressure may be used to return the cylinder 41.

A significant feature of the present invention is the utilization ofonly the pump means 23 to power the influent control valve 40 shown inFIGS. 3 and 8. Dependent on the level of the float, the valve 44regulates the pressure in actuating cylinder 41 thus moving the valve 40to a compensating position. In the absence of pressure as might occur ona pump failure, the valve 40 is held closed. When the influent valve isclosed, it is impossible to flood the filter of the present inventionand to have spillage. Thus, a fail safe arrangement is provided wherebyinfluent is introduced to the filter 10 only when the pump 23 continuesremoving purified liquid from the filter 10. Thus, the sole source ofpower is the power required for the pump motor 24. Other sources ofenergy are not required for the present invention.

Continuing the description of FIGS. 3 and 8 together, it will be notedthat a small hand-operated valve directs liquid under pressure through aconduit 51 into a chemical additive tank indicated by the numeral 52.The tank 52 is adapted to receive a quantity of chemical additives whichtypically enhance operation of the filter 10 of the present invention.The chemicals may be in dry powder form, may be a wet slurry, or may beconcentrated liquid. Numerous chemical additives which enhance thefiltration process such as flocculants may be customarily added,depending on the particular liquid and impurities to be filtered. Ofcourse, the apparatus may be liquid with the chemicals to carry thesuspended or dissolved chemicals into the nozzle 16 to be introducedinto the settling basin 18. The chemicals are dispersed in the liquid inthe filter 10 and serve their purpose in the customary or intendedmanner. Dependent on the setting in the valve 50 and the measure ofchemicals placed in the container 15, a controlled rate of introductionof the chemical to the filter 10 is obtained through the arrangementshown above. Of particular interest is the fact that no separate motivemeans is required for operation of the ratably controlled chemicalinduction system. Again, it is dependent on the continued operation ofthe pump 23 shown in the drawing. Hence, a failure of the pump 23 leadsto a complete shut down of the equipment shown in FIGS. 3 and 8, andprevents undesirable accidents through the use of the present invention.

As mentioned several times in the present disclosure, the liquidintroduced to the filter 10 is sometimes laden with heavy suspendedparticles and with lighter impurities, typically oil, which is suspendedin the liquid. While the heavier particles settle out and are disposedof in the manner to be described, the lighter contaminants float to thesurface. In FIG. 6, the apparatus removing the lighter impurities isshown. Briefly, the liquid level rises to enter the skimming apparatus.The numeral 60 indicates a skimmer box which is positioned at a levelaccommodating the range of levels of the liquid 17 in the filter 10. Afloat 61 buoys up a skimming weir 62 which is hinged to the skimmer box60. The upper edge of the weir 62 is just below the level of the liquidso that a thin sheet of water spills over the skimming weir into theskimmer box proper. The weir 62 is hinged to the lower portions of thebox 60 to permit it to rise and fall with the various liquid levels inthe filter apparatus 10. The dotted line position of the weir 62 shownin FIG. 6 illustrates the range of movement of the weir 62. As the waterlevel rises, the float 61 carries the weir 62 toward its uprightposture, all the while a thin sheet of impurities in the water spillingover the top edge of the weir. The thin layer of water spilling over theweir typically will carry oil or flotsom into the skimmer box chamberfor disposal.

The numeral 63 indicates the control handle of a valve 64 in the skimmerbox 60. The valve 64 communicates with an overflow pipe 65 whichprovides for waste disposal. It will be noted that the very upper end ofthe overflow pipe 65 is located to drain the skimmer box 60 should thelevel rise too high. The valve 64 is adjusted to drain the skimmer box60 at a controlled rate dependent on the quantity of impurities skimmedfrom the surface of the water.

The foregoing describes that portion of the apparatus which removes thelighter contaminants carried in the water 17. FIG. 6 also illustrates inenlarged detail the apparatus for removing heavier contaminants from thestilling well 18. The sediment well 37 previously described with regardto FIG. 2 is included in FIG. 6. As mentioned before, heavier particlestend to settle into the well 37. The apparatus includes a lift tube 70having an open mouth in the waste trough 37. A jet nozzle 71 injectsfluid upwardly into the lift tube 70. The nozzle 71 is communicated by aconduit 72 with a control valve 73 which admits liquid under pressurefrom the tubing 416 shown in FIG. 1. It is quite important to note thatthe conduit 46 is communicated with the pump 23. The disposal apparatusfor the heavier sediment is powered solely from the pump 23. Hence, theapparatus functions so long as the equipment as a whole is operative andthe need for extraneous connections of power means to the presentapparatus is thereby avoided. While an independent power means may beused, the foregoing is considered a virtue and an independent powermeans would be adopted only for special purposes or reasons.

In any event, the jet '7! is directed upwardly in the draw pipe 70. Thevalve 73 is preferably an inspirator valve of a nature believed readilyknown to those skilled in the art. The inspirator valve inducts air intothe fluid flow which tends to reduce the specific gravity of the liquidin the draw pipe 70 and creates an upward flow. The heavy sediment inthe sediment basin 37 is lifted in the draw pipe 70 and when mixed withthe upwardly directed stream of air and water from the jet 71, thecombined liquids have a lower fluid density and hence flow up the lifttube 70 toward a compensating level. However, the draw pipe 70 is curvedat the portion 74 and is downwardly directed at 75 into the wasteoverflow pipe 65. An air vent 76 releases bubbles entrained in theliquid flow, thereby increasing the density of the mixture causing it toreadily drop into the waste overflow pipe 65. The pipe 65 carries awaythe waste from the draw pipe 70. It should be noted that the sedimenttrough 37 is communicated by way of a normally closed valve 77communicating with the waste pipe 65. Should the occasion arise at whicha draining of the sediment basin 37 is desired, the valve 77 may bebriefly opened and the large rate of flow will quickly clean the bottomof the tank.

The foregoing has described the various and sundry components of thepresent invention, and more particularly, has directed attention to thevarious features of the present invention. The several features shouldbe considered cooperatively and a greater understanding of the presentinvention will be obtained by tracing through the operation of thepresent invention. As mentioned before, the apparatus is assumed to becooperative with a plant for purification of the water, which has bothheavier and lighter trash or sediment in the water as well as forpurposes of removing various suspended impurities. Of course, theapparatus may be used with other liquids to remove many otherimpurities.

In operation, the control valve 40 is connected with a source of liquidto be purified. The liquid is admitted to the filter system I0 throughthe nozzle 16 and begins to fill the stilling well 118. AS the level ofthe liquid rises within the stilling well, the heavier sediment fallsout toward the sediment trough 37 as previously described. Also, thelighter impurities in the liquid rise to the upper surface for removalby the skimming apparatus shown clearly in FIGS. 6 and 7. Of course, thebaffle grid 20 communicates the liquid to the filter nest forpurification =by the apparatus. The pump 23 draws liquid through thefilter nest and the various individual filter elements in the nest. Thepurified water is collected in the header 22 drawn by the suction of thepump 23 and is delivered through the outlet header 26. The filterelements remove the suspended impurities in the manner described above,it being noted that the surfaces of the various filter elements areprotected by the absence of clogging impurities. By clogging impurities,reference is had to the effect of trash or oil on the screen surfaces,to name a few of several clogging impurities.

The lighter impurities or contaminants skimmed from the surface and theheavier sediment collected at the bottom of the apparatus are removedthrough the waste disposal tube 65 as described. The absence of theseimpurities from the water passing through the filter itself isparticularly beneficial. The

liquid is permitted a greater interval of time at the cleaning surfaces,which markedly improves the quality of operation of the apparatus. Thereis measurably less tendency of the filter surfaces to form a skin ofimpurities tending to block further operation of the filters and, thereis typically little or no coagulation of the various impurities as mightoccur when many impurities adhere to oil droplets or the like.

A particular benefit of the present invention is the utilization of anopen top apparatus. This avoids the manufacturing requirements of apressurized vessel with the essential gaskets and other sealing members.More particularly, this permits a visual inspection of the apparatusduring its operation. Thus, a visual inspection of the skimmer box isreadily had. Likewise, the baffle grid 20 may be inspected to be certainthat large debris is not collected thereon, indicating an overloading ofthe system. Should one of the particular filters become faulty inoperation, it is readily removed from the apparatus. This requiresremoval of the baffle grid 20 if used and disconnection of the clips 311as shown in FIG. 5. The individual filter may be removed and the openingin the collection header 22 is either plugged or a new filter connectedto it. In either case, this can be done while the apparatus continues tooperate. Removal of the individual filters in the manner described aboveis enhanced upon hinging the baffle grid 20 to the balfle wall 119 topermit its movement to an upright position. This continues its functionin that it continues to define the settling well 18. Should servicing inthe above manner be envisioned as a matter of routine, the return nozzle20 can either be formed of a flexible material or can be hinged topennit it to swing upwardly and out of the way of the individual filtersas they are removed. Thus, the filter immediately adjacent the end wall12 shown in FIGS. 1 and 2 can be readily serviced and removed in thismanner.

The foregoing is directed to the preferred embodiment of the presentinvention. As will be understood, the apparatus can be used with wateror other liquids and various and sundry impurities of all types andkinds. Moreover, the apparatus may be moderately small or can be quiteexcessive in size to provide a very large volume of filtration. Forinstance, in a larger installation, it may be necessary to duplicate thefilter nest on individual headers which all communicate with a singlepump. Thus, several groups of filters may be located across the width ofthe apparatus. Also, the skimmer weir can be enlarged and expanded fromthat as shown in the drawings. This also depends on the filtrationvolume required. A particularly important feature of the presentinvention is the dependency of all portions thereof on a single powersource. When the motor 24 fails to operate for any reason, or the pump23 becomes inoperative, all portions of the apparatus cease to operateand, more importantly, the valve 40 is closed to prevent the furtherinduction of influent. As a consequence, no alternative, supportive, orauxiliary sources of power are required .by the apparatus. This featureis believed particularly important in most installations inasmuch as asingle check of the operative condition of the pump 23 suffices toprovide information as to the operative nature of the entire system.

While many other objects and advantages of the present invention willbecome more readily apparent from a reading of the foregoing, the termsadopted herein are extended to the claims appended hereto.

What is claimed is:

I. Liquid-filtering apparatus adapted for filtering liquids removingimpurities of greater and lesser density therefrom and comprising: anopen vessel having upright sides and a closed bottom and adapted forreceiving liquids; a filtered effluent header cooperatively arranged insaid vessel above said vessel bottom and having at least one openingtherein; diatomaceous filtering means including at least onediatomaceous filtering element arranged in a generally upright positionwithin said vessel and having an outlet fluidly coupled to said headeropening for conducting liquids strained through said filtering elementinto said header, and means adapted for selectively coating saidfiltering element with a diatomaceous filtering agent; a liquid pumphaving a discharge line and a suction line fluidly coupled to saidheader and adapted for drawing liquids through said filtering elementinto said header and suction line for delivery by said discharge line atan elevated pressure; liquid supply means adapted for supplyingunfiltered liquids to said vessel in sufficient quantity to fill saidvessel to a level above said filtering element and including a liquidinlet, and means cooperatively associated with said vessel for definingan open liquid retention well between said filtering element and saidliquid inlet for quieting unfiltered liquids entering said retentionwell before such liquids are drawn through said filtering element; andimpurity separating means on said vessel adapted for separating fromsuch supplied liquids impurities carried thereby having densitiesdifferent than such liquids and including a sediment collection basin inthe bottom of said retention well adapted for collect ing sedimentsfalling to the bottom of said retention well as liquids pass throughsaid retention well to said filtering element, a sediment withdrawalconduit cooperatively arranged in said sediment collection basin andextended out of said retention well, an air inspirator exterior of saidretention well fluidly coupled to said pump discharge line and adaptedfor drawing air into liquids supplied to said air inspirator by saidliquid pump, and a conduit coupled to the outlet of said air inspiratorand terminated in said sediment withdrawal conduit adjacent to saidsediment collection basin for delivering airbearing liquid into saidsediment withdrawal conduit whereby the hydrostatic head of liquids insaid retention well will discharge sediment-bearing liquids through saidsediment withdrawal conduit to the exterior of said retention well uponoperation of said liquid pump.

2. The filtering apparatus of claim 1 wherein said impurity separatingmeans further include a collection tank adjacent to said retention well,and weir means cooperatively arranged between said collection tank andsaid retention well for drawing impurities floating on the surface ofliquids in said retention well into said collection tank.

3. The filtering apparatus of claim 2 wherein said weir means include aweir member, means supporting said weir member for movement betweenvertically spaced positions, and a liquid float coupled to said weirmember and adapted for locating said weir member at its said spacedpositions in accordance with the level of liquids in said collectiontank.

4. The filtering apparatus of claim 1 further including chemical supplymeans adapted for supplying chemicals to unfiltered liquids enteringsaid retention well, said chemical supply means including achemical-holding tank mounted above said liquid inlet, an uprighttubular shaft rotatably journaled in said holding tank and extendeddownwardly into said liquid inlet and adapted for carrying chemicalsfrom said holding tank into said liquid inlet, an impeller mounted onthe upper portion of said shaft within said holding tank, and a watersupply line coupled to said pump discharge line and cooperativelyterminated adjacent to said impeller for rotatably driving said impellerand said shaft as chemicals are discharged from said holding tank intosaid tubular shaft for delivery to said liquid inlet.

5. The filtering apparatus of claim 4 wherein said impurity separatingmeans include a collection tank adjacent to said retention well, andweir means cooperatively arranged between said collection tank and saidretention well for drawing impurities floating on the surface of liquidsin said retention well into said collection tank.

6. The filtering apparatus of claim 5 wherein said weir means include aweir member, means supporting said weir member for movement betweenvertically spaced positions, and a liquid float coupled to said weirmember and adapted for locating said weir member at its said spacedpositions in accordance with the level of liquids in said collectiontank.

7. The filtering apparatus of claim 5 further including valve meansfluidly coupled to said liquid inlet, and liquid level control meanscooperatively coupled to said valve means for operating said valve meansin accordance with the level of lrqurds rn said retention well forcontrolling the entrance of liquids into said liquid inlet.

1. Liquid-filtering apparatus adapted for filtering liquids removing impurities of greater and lesser density therefrom and comprising: an open vessel having upright sides and a closed bottom and adapted for receiving liquids; a filtered effluent header cooperatively arranged in said vessel above said vessel bottom and having at least one opening therein; diatomaceous filtering means including at least one diatomaceous filtering element arranged in a generally upright position within said vessel and having an outlet fluidly coupled to said header opening for conducting liquids strained through said filtering element into said header, and means adapted for selectively coating said filtering element with a diatomaceous filtering agent; a liquid pump having a discharge line and a suction line fluidly coupled to said header and adapted for drawing liquids through said filtering element into said header and suction line for delivery by said discharge line at an elevated pressure; liquid supply means adapted for supplying unfiltered liquids to said vessel in sufficient quantity to fill said vessel to a level above said filtering element and including a liquid inlet, and means cooperatively associated with said vessel for defining an open liquid retention well between said filtering element and said liquid inlet for quieting unfiltered liquids entering said retention well before such liquids are drawn through said filtering element; and impurity separating means on said vessel adapted for separaTing from such supplied liquids impurities carried thereby having densities different than such liquids and including a sediment collection basin in the bottom of said retention well adapted for collecting sediments falling to the bottom of said retention well as liquids pass through said retention well to said filtering element, a sediment withdrawal conduit cooperatively arranged in said sediment collection basin and extended out of said retention well, an air inspirator exterior of said retention well fluidly coupled to said pump discharge line and adapted for drawing air into liquids supplied to said air inspirator by said liquid pump, and a conduit coupled to the outlet of said air inspirator and terminated in said sediment withdrawal conduit adjacent to said sediment collection basin for delivering air-bearing liquid into said sediment withdrawal conduit whereby the hydrostatic head of liquids in said retention well will discharge sediment-bearing liquids through said sediment withdrawal conduit to the exterior of said retention well upon operation of said liquid pump.
 2. The filtering apparatus of claim 1 wherein said impurity separating means further include a collection tank adjacent to said retention well, and weir means cooperatively arranged between said collection tank and said retention well for drawing impurities floating on the surface of liquids in said retention well into said collection tank.
 3. The filtering apparatus of claim 2 wherein said weir means include a weir member, means supporting said weir member for movement between vertically spaced positions, and a liquid float coupled to said weir member and adapted for locating said weir member at its said spaced positions in accordance with the level of liquids in said collection tank.
 4. The filtering apparatus of claim 1 further including chemical supply means adapted for supplying chemicals to unfiltered liquids entering said retention well, said chemical supply means including a chemical-holding tank mounted above said liquid inlet, an upright tubular shaft rotatably journaled in said holding tank and extended downwardly into said liquid inlet and adapted for carrying chemicals from said holding tank into said liquid inlet, an impeller mounted on the upper portion of said shaft within said holding tank, and a water supply line coupled to said pump discharge line and cooperatively terminated adjacent to said impeller for rotatably driving said impeller and said shaft as chemicals are discharged from said holding tank into said tubular shaft for delivery to said liquid inlet.
 5. The filtering apparatus of claim 4 wherein said impurity separating means include a collection tank adjacent to said retention well, and weir means cooperatively arranged between said collection tank and said retention well for drawing impurities floating on the surface of liquids in said retention well into said collection tank.
 6. The filtering apparatus of claim 5 wherein said weir means include a weir member, means supporting said weir member for movement between vertically spaced positions, and a liquid float coupled to said weir member and adapted for locating said weir member at its said spaced positions in accordance with the level of liquids in said collection tank.
 7. The filtering apparatus of claim 5 further including valve means fluidly coupled to said liquid inlet, and liquid level control means cooperatively coupled to said valve means for operating said valve means in accordance with the level of liquids in said retention well for controlling the entrance of liquids into said liquid inlet. 